Weapon
Origins The first Demon Weapons were created 800 years ago prior to the start of the series by the Witch Arachne, following instructions found within the Book of Eibon. To create a Demon Weapon she murdered a fellow Witch to use as a sacrifice. Using the Witch's soul which has the power of transformation Arachne joined together an inanimate weapon and a human soul to create a Demon Weapon which had the ability to transform from Human to Weapon form. This act of killing her own kind labeled her as "The Heretic Witch" and caused her to be hunted by both Shinigami and Witch alike. The blood of a Weapon is passed down through genetics, however depending on the circumstances of an individuals life that blood may or may not actually be awakened. There are families like the Nakatsukasa clan which are made up entirely of Weapons, and families like the Evans family where the Weapons Soul and Danni are apparently the only members to have inherited the Weapon blood for numerous generations. Abilities Humans with active Weapon genes have the ability to change their entire body into some variety of a weapon. When becoming a weapon, their clothing and everything on their person is carried on into the transformation. After becoming a weapon, the person is seen in his/her human form as some sort of reflection on the weapon and is seen in a completely black space when viewed inside the weapon. Often, in this dark space they are seen without their clothing on, save for a few details (Harvar appears with his visor on). In other cases they can be seen with their entire clothing. The Weapons also glow in the color of their souls when inside Weapon Form. For example, Soul Eater has a blue soul, as such, he glows blue when transforming. Tsubaki has a yellow soul, therefore she glows yellow. The Thompson sisters have pink souls, so they glow pink. This glow is also present when the Weapons are transforming. Some Weapons in their Weapon Form have certain components that move similarly to facial expressions; such as Soul, whose Weapon Form has a red eye on top of the haft, which can convey his mood by narrowing when he is angry or ready to fight, or widening when he is startled. Ragnarok's Weapon Form has a mouth on the blade near the guard. Most Weapons can also transform parts of their body (mostly their arms) into Weapon Form to enhance lethality in battle, however with the exception of a few Autonomous weapons, most are stronger when being paired with a Meister. It seems that transforming parts of their bodies into weapons doesn't affect their clothing either, as Spirit can easily sprout blades from his arms and back without tearing his clothes, and Soul can turn his entire arm into a blade with similar effect. When paired with a Meister, a Weapon becomes extremely deadly. By performing resonance between a Meister and a Weapon, the Weapon can unleash a variety of abilities and can even change its physical form. There is apparently no restriction on who is capable of wielding a Weapon, even another Weapon, but when a specific Weapon is wielded by someone who cannot effectively resonate with them, a rejection reaction occurs. This reaction is derived from a misalignment in the users' Soul Wavelengths, resulting from incompatible personalities, and appears to differ depending upon the individuals involved. For a Weapon and Meister to be compatible, they have to be able to accept and understand each others' personalities. Most compatible Weapon and Meister pairs seem to be opposites in personalities, especially seen with Black Star and Tsubaki and Ox and Harvar. People with similar personalities like Soul and Black Star cannot become an efficient team. So far, Soul and Ragnarok are the only ones to show a rejection reaction though. Symptoms of this rejection seems to vary on how much the Wavelengths are incompatible. When Black Star tried to wield Soul, their Wavelengths were so incompatible, that Black Star could not even lift Soul from the ground, and when Black Star sent his Wavelength through him, it caused the Demon Scythe physical harm. In the brief moment when Maka couldn't resonate with Soul, the rejection reaction was milder, but still harmful, as even though Maka was able to wield Soul, his Weapon Form was extremely hot to the touch and she severely burnt her hands until she could resonate with him again. Ragnarok's rejection reaction effects Crona as well as they both share the same body, and when their Wavelengths become misaligned, dozens of Bloody Needles erupt uncontrollably from Crona's body and the pair loses their ability to utilize their Black Blood.